As shown in PTL 1 (Japanese Unexamined Patent Application Publication No. 2006-198735), conventionally, a coated tool (hereinafter referred to as a conventional coated tool 1) is known which is formed by vapor-depositing, on the surface of a tool substrate (hereinafter generally referred to as a tool substrate) made of tungsten carbide (hereinafter referred to as WC)-based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN)-based cermet, a hard-coating layer including a lower layer (a) and an upper layer (b) satisfying the following conditions.
The lower layer (a) is a Ti compound layer composed of one or more of a titanium carbide (TiC) layer, a titanium nitride (TiN) layer, a titanium carbonitride (TiCN) layer, a titanium carboxide (TiCO) layer and a titanium oxycarbonitride (TiCNO) layer, and having a total mean layer thickness of 3 to 20 μm.
The upper layer (b) is an α-type Al2O3 layer (referred to as a conventional α-type Al2O3 layer) having a mean layer thickness of 1 to 15 μm and having an α-type crystal structure in a chemically vapor-deposited state. As for this upper layer, when the field-emission-type scanning electron microscope is used to individually irradiate crystal grains having a hexagonal crystal lattice present within the measurement range of a polished surface with an electron beam, and to measure the tilt angle of the normal lines of the (0001) plane and plane (10-10), which are crystal planes of the crystal grains, to the normal line to the polished surface; the crystal grains have a corundum hexagonal close-packing structure in which the constituent atoms composed of Al and oxygen are present at lattice points; the distribution of lattice points (constituent atom sharing lattice points) where the respective constituent atoms share one constituent atom between the crystal lattices at an interface between mutually adjacent crystal grains is calculated on the basis of the resulting measured tilt angles; and a constituent atom sharing lattice point configuration in which N (here, N is any even number equal to or greater than 2 in a crystal structure of a corundum-type hexagonal close-packing crystal, but when the upper limit of N is 28 from the viewpoint of a distribution frequency, even numbers 4, 8, 14, 24, and 26 do not exist) lattice points which do not share any constituent atoms between the constituent atom sharing lattice points are present is expressed by ΣN+1, this layer shows a constituent atom sharing lattice point distribution graph in which the highest peak is present in Σ3 in the constituent atom sharing lattice point distribution graph showing distribution ratios in which individuals of ΣN+1 are accounted for in a total of ΣN+1, and the distribution ratio of Σ3 accounted for in the total of ΣN+1 is 60 to 80%.
Since the α-type Al2O3 layer has excellent high-temperature strength, it is known that the conventional coated tool 1 exhibits chipping resistance in high-speed intermittent cutting work.
As shown in PTL 2 (Japanese Unexamined Patent Application Publication No. 2006-289556), instead of the upper layer (b) of the conventional coated tool 1, a coated tool (hereinafter referred to as a conventional coated tool 2) in which an Al—Ti compound oxide layer (hereinafter referred to as a conventional AlTiO layer) is formed is also known.
The Al—Ti compound oxide layer has a mean layer thickness of 1 to 15 μm, and an α-type crystal structure in a chemically vapor-deposited state. This layer satisfies the compositional formula, (Al1-XTiX)2O3, where X ranges from 0.003 to 0.05 in atomic ratio. Moreover, as for this layer, when the field-emission-type scanning electron microscope and an electronic backscattering diffraction image apparatus are used to individually irradiate crystal grains having a hexagonal crystal lattice present within the measurement range of a polished surface with an electron beam, and to measure the tilt angle of the normal lines of the (0001) plane and plane (10-10), which are crystal planes of the crystal grains, to the normal line to the surface of a base; the crystal grains have a corundum hexagonal close-packing structure in which constituent atoms composed of Al, Ti and oxygen are present at lattice points; the distribution of lattice points (constituent atom sharing lattice points) where the respective constituent atoms share one constituent atom between the crystal lattices at an interface between mutually adjacent crystal grains is calculated on the basis of the resulting measured tilt angles; and a constituent atom sharing lattice point configuration in which N (where N is any even number equal to or greater than 2 in a crystal structure of a corundum-type hexagonal close-packing crystal, but when the upper limit of N is 28 from the viewpoint of a distribution frequency, even numbers 4, 8, 14, 24, and 26 do not exist) lattice points which do not share any constituent atoms between the constituent atom sharing lattice points are present is expressed by ΣN+1, this layer shows a constituent atom sharing lattice point distribution graph in which the highest peak is present in Σ3 in the constituent atom sharing lattice point distribution graph showing distribution ratios in which individuals of ΣN+1 are accounted for in a total of ΣN+1, and the distribution ratio of Σ3 accounted for in the total of ΣN+1 is 60 to 80%.
It is known that this conventional coated tool 2 also exhibits excellent chipping resistance.
As shown in PTL 3 (Japanese Unexamined Patent Application Publication No. 2004-1154), instead of the upper layer (b) of the conventional coated tool 1, a coated tool (hereinafter referred to as a conventional coated tool 3) in which an α-type (Al, Y)2O3 layer (hereinafter referred to as a conventional AlYO layer) containing a small amount of Y (yttrium) is formed is also known. In this conventional coated tool 3, it is known that missing out of the crystal grains of α-type Al2O3 is prevented, and excellent cutting durability is shown in continuous cutting work.
As shown in PTL 4 (Japanese Unexamined Patent Application Publication No. 2006-289557), instead of the upper layer (b) of the conventional coated tool 1, a coated tool (hereinafter referred to as a conventional coated tool 4) in which an Al—Zr compound oxide layer (hereinafter referred to as a conventional AlZrO layer) is formed is also known. The Al—Zr compound oxide layer has an α-type crystal structure, and a mean layer thickness of 1 to 15 μm in a chemically vapor-deposited state, and satisfies the compositional formula, (Al1-XZrX)2O3, where X ranges from 0.003 to 0.05 in atomic ratio. As for the Al—Zr compound oxide layer, when the field-emission-type scanning electron microscope is used to individually irradiate crystal grains having a hexagonal crystal lattice present within the measurement range of a polished surface with of a base with an electron beam, and to measure the tilt angle of the normal lines of the (0001) plane and plane (10-10), which are crystal planes of the crystal grains, to the normal line to the surface of the base; the crystal grains have a corundum hexagonal close-packing structure in which constituent atoms composed of Al, Zr and oxygen are present at lattice points; the distribution of lattice points (constituent atom sharing lattice points) where the respective constituent atoms share one constituent atom between the crystal lattices at an interface between mutually adjacent crystal grains is calculated on the basis of the resulting measured tilt angles; and a constituent atom sharing lattice point configuration in which N (here, N is any even number equal to or greater than 2 in a crystal structure of a corundum-type hexagonal close-packing crystal, but when the upper limit of N is 28 from the viewpoint of a distribution frequency, even numbers 4, 8, 14, 24, and 26 do not exist) lattice points which do not share any constituent atoms between the constituent atom sharing lattice points are present is expressed by ΣN+1, this layer shows a constituent atom sharing lattice point distribution graph in which the highest peak is present in Σ3 in the constituent atom sharing lattice point distribution graph showing distribution ratios in which individuals of ΣN+1 are accounted for in a total of ΣN+1, and the distribution ratio of Σ3 accounted for in the total of ΣN+1 is 60 to 80%.
It is known that this conventional coated tool 4 also exhibits excellent chipping resistance.
As shown in PTL 5 (Japanese Unexamined Patent Application Publication No. 2006-289586, a coated tool (hereinafter referred to as a conventional coated tool 5) is known which is formed by vapor-depositing, on the surface of a tool substrate made of tungsten carbide (hereinafter referred to as WC)-based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN)-based cermet, a hard-coating layer including following lower layer (a) and upper layer (b).
The lower layer (a) is a Ti compound layer composed of one or more of a titanium carbide (TiC) layer, a titanium nitride (TiN) layer, a titanium carbonitride (TiCN) layer, a titanium carboxide (TiCO) layer and a titanium oxycarbonitride (TiCNO) layer, all of which are formed by vapor deposition, and having a total mean layer thickness of 3 to 20 μm, and
The upper layer (b) is a Cr-containing aluminum oxide layer having a mean layer thickness of 1 to 15 μm and having an α-type crystal structure in a chemically vapor-deposited state. As for this upper layer, when the field-emission-type scanning electron microscope is used to individually irradiate crystal grains having a hexagonal crystal lattice present within the measurement range of the polished surface of the tool substrate with an electron beam, and to measure the tilt angle of the normal line to the (0001) plane, which is a crystal plane of each crystal grain, to the normal line to the polished surface, the measured tilt angles which are within a range of 0 to 45 degrees among the measured tilt angles are divided at every pitch of 0.25 degrees, and a tilt angle frequency distribution graph obtained by summing the frequencies present within the respective divisions is plotted, this layer shows a tilt angle frequency distribution graph in which the highest peak is present in the tilt angle division within a range of 0 to 10 degrees, and the total sum of the frequencies present within a range of 0 to 10 degrees accounts for the ratio of 45% or more of the total frequency in the tilt angle frequency distribution graph.
Since the Cr-containing aluminum oxide layer has excellent high-temperature strength, it is known that the conventional coated tool 5 exhibits chipping resistance in high-speed intermittent cutting work.